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January is Glaucoma Awareness Month. Although there are many awareness and appreciation months and days associated with silliness (did we truly need a National Beer Can Appreciation Day on January 24?), Glaucoma Awareness Month is not one of them. Glaucoma is not uncommon in dogs, and it’s a big deal. Dog owners need to be aware of this potential problem.

Two or three years ago, a couple brought their Cocker Spaniel to my office at 10 p.m. The dog had a one-day history of squinting the right eye. The eye also was red and cloudy. There had been no known trauma, and the dog had not been to an area where foxtails or other possible foreign bodies were prevalent.

The eye in question was clearly uncomfortable. The dog was reluctant to open his eye (which is a sign of eye pain), and he winced when I got near it. After I applied a numbing agent to the eye, I was able to assess it more carefully. The white portion of the eye had become inflamed, and there were many angry blood vessels coursing along it, causing it to look red. The cornea, which lies on the surface of the eye over the pupil and normally is clear and colorless, had turned cloudy and blue. Such discoloration is called corneal edema, and it is a sign of inflammation. The cloudiness made it impossible to see the pupil or the deeper structures in the eye.

The owners agreed to let me run some tests on the eye. Gentle probing did not reveal evidence of a foreign body. A fluorescent dye applied to the eye showed no signs of trauma to the eye’s surface. But when I measured the pressures in each eye, the cause of the trouble became clear. The pressure in the right eye was 60 mm of mercury (mm of mercury is a convention used for measuring eye pressures). Normal pressures are about a third of that.

The dog had acute glaucoma.

In general, I try to appreciate that most life circumstances are composed of shades of grey and not black and white. A dog with vomiting and diarrhea will be best served by aggressive therapy, but he may get through with less treatment. However, in veterinary medicine, a few conditions are black and white. A dog with gastric dilatation and volvulus (GDV, known colloquially as bloat) will die within hours unless he has surgery. And a dog with acute glaucoma rapidly will go permanently blind in the affected eye without treatment.

I broke the bad news to the owners. One of them seemed a bit incredulous when she heard my recommendation: hospitalize the dog overnight for aggressive topical and intravenous anti-glaucoma therapy. What would happen, she wondered, if she just kept an eye on the problem overnight instead?

She did not like my answer: If no treatments were performed, the dog would almost certainly be permanently blind in the eye by the morning. The owners asked for a moment to confer in private.

They did more than consult with each other. They also got in touch with Dr. Google. When I first started practicing medicine, Dr. Google was notoriously inaccurate. Flat Earthers and holocaust deniers seemed to get equal weight as legitimate experts. Things have improved substantially in the intervening 16 years.

When I reentered the exam room, the sobbing client looked up from her iPhone and almost threw her dog at me, begging me to hurry with the treatment.

What exactly was happening to the dog, and why was it such a big deal? The eye is filled with fluid that is produced in one area, circulates around, and then drains out. If too much fluid is produced or, as is more common, the fluid does not drain properly, then excess fluid accumulates in the eye. This causes an increase in pressure in the eye.

That increased pressure hurts, so the first sign of acute glaucoma usually is squinting, which is how dogs and people respond to eye pain. To make things worse, it doesn’t take long for the pressure to start damaging the eye. The eye will become cloudy and red. However, the inflammation that occurs on the surface of the eye is not the real area of concern. What really matters is what damage to the retina, or the back of the eye.

The retina is where vision cells are located. They, and the nerve cells that course through the retina, are extremely fragile. Very high eye pressure can kill them within hours, and they don’t regenerate. In other words, severe acute glaucoma can result in permanent blindness within hours.

The most common form of glaucoma in dogs results in acute glaucoma in most cases. It appears to have a strong hereditary component, and many breeds (including Cocker Spaniels, Basset Hounds, Schnauzers, Greyhounds, and most of the Arctic breeds) have a predisposition to the condition. It generally develops in only one eye at first, but the second eye is likely to become affected in a time frame that ranges from days to years.

The Cocker Spaniel was admitted to the hospital and STAT bloodwork was run to ensure that he did not have kidney disease (which precludes use of mannitol, the most common intravenous medication used for acute glaucoma). He received two doses of mannitol and one dose of dexamethasone intravenously. Intravenous pain killers were administered. We commenced topical anti-glaucoma eye drops as well.

Two hours later the pressure in the eye was 20. He was markedly more comfortable. Happily, the dog also appeared able to see in the eye. I sent him off to a specialist in veterinary ophthalmology as soon as the office opened in the morning.

The dog retained sight in the affected eye that night. But if the owners hadn’t acted quickly, things would not have turned out so well. The eye would have become permanently blind. The eye, over time, would have swollen out of the socket. The pain would have been unrelenting, and ultimately the only treatment would have been to remove the eye in order to eliminate the source of the pain.